Defects during the casting process are not uncommon. Under practical conditions, all casting products contain voids, inclusions and other imperfections which contribute to a normal quality variation. Such imperfections begin to be regarded as true defects or flaws only when the satisfactory function or appearance of the product is in question: consideration must then be given to the possibility of salvage or, in more serious cases, to rejection and replacement.<\/p>\n
Classification<\/strong><\/p>\n The general origins of defects lie in three sectors: Standardization and optimisation of all aspects of the production technique offers the best way-out against such troubles. More specific precautions can be taken in those cases where there is a known susceptibility to a particular defect, whilst the radical approach of design modification may need to be considered in the extreme cases which do not respond to changes in foundry technique. It should be clear that any approach to the elimination of casting defects must be on an economic basis.<\/p>\n 1. Shaping faults arising in pouring. Significance of analysis of defects<\/strong><\/p>\n Casting defects, whatever their cause, cannot be considered in isolation; their significance can only be established in relation to the function of the casting. Behaviour under service stresses and environment is in most cases the important reason behind the appearance.<\/p>\n What are the reasons of their occurrence? The first one is the Defects during the casting process are not uncommon. Under practical conditions, all casting products contain voids, inclusions and other imperfections which contribute to a normal quality variation. Such imperfections begin to be regarded as true defects or flaws only when the satisfactory function or appearance of the product is in […]<\/p>\n","protected":false},"author":1,"featured_media":2886,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_mi_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"_joinchat":[]},"categories":[10],"tags":[],"yoast_head":"\n
\n1. the casting design,
\n2. the technique of manufacture\u2013the method,
\n3. the application of the technique\u2013\u2018workmanship\u2019.<\/p>\n
\n2. Inclusions and sand defects.
\n3. Gas defects.
\n4. Shrinkage defects due to volume contraction in the liquid state and during solidification.
\n5. Contraction defects occurring mainly or wholly after solidification.
\n6. Dimensional errors.
\n7. Compositional errors and segregation.<\/p>\n
\nquality and the parameters of moulding and core mixtures. Number of the
\ndefects was affected by temperature and humidity of ambient air, both in
\nstore yards and in moulding mixture preparation shop. Consequently, it is
\nreflected in moisture content of silica sand and moulding mixture. This fact
\ncan affect the quality of moulding and core mixtures and their prone to
\ndisintegration by molten metal flow.
\nThe second one is the presence of complicated design of the cavity in the mould,
\ncontaining thin walls, profiles, runners. From this fact follows the necessity
\nto design parameters of moulding mixtures from the mould complexity
\npoint of view.
\nThe third one is chemistry and pouring temperature of molten metal.
\nViscosity of poured metal is extremely important.<\/p>\n","protected":false},"excerpt":{"rendered":"